1. Field of the Invention
The present invention relates to a light-emitting diode (LED) chip. More particularly, the present invention relates to a LED chip where a current distribution therein can be adjusted.
2. Description of Related Art
With development of semiconductor technology, a present LED may achieve a high-brightness output, and since the LED has advantages of power-saving, small-size, low power driving and non-mercury, etc., it has been widely used in displays and illumination devices, etc. Generally, a light-emitting efficiency of a LED chip relates to internal quantum efficiency (i.e. light-extraction efficiency) of the LED chip. When the light emitted from a light-emitting layer has a higher transmittance with respect to the LED chip, it represents that the LED chip has good light-emitting efficiency.
Electrodes of the LED chip are generally fabricated by metal materials, and since the metal materials are opaque, the light emitted from a region under the electrode of the LED chip may be blocked, which may cause a waste of power. Therefore, a technique of forming a current blocking layer between the electrode and the semiconductor device layer is developed.
FIG. 1A is top view of a conventional LED chip having a current blocking layer. FIG. 1B is a cross-sectional view of the LED chip of FIG. 1A along the I-I′ line. Referring to FIG. 1A and FIG. 1B, the LED chip 100 includes a substrate 110, a semiconductor device layer 120, a current blocking layer 130, a current spread layer 140, a first electrode 150 and a second electrode 152. The semiconductor device layer 120 includes a first type semiconductor layer 122, a light-emitting layer 124 and a second type semiconductor layer 126.
As shown in FIG. 1A and FIG. 1B, the second electrode 152 is disposed on the first type semiconductor layer 122. The first electrode 150 is disposed on the second type semiconductor layer 126, and the current blocking layer 130 is disposed between the first electrode 150 and the second type semiconductor layer 126. Moreover, the current spread layer 140 is disposed between the first electrode 150 and the second type semiconductor layer 126, and covers the current blocking layer 130 entirely, wherein a shape of the current blocking layer 130 and a shape of the first electrode 150 are similar figures, and an area of the current blocking layer 130 is slightly greater than that of the first electrode 150. The current blocking layer 130 is used to block the current passing through an area covered by the current blocking layer 130. If the LED chip 100 does not have the current blocking layer 130, the light emitted from the light-emitting layer 124 under the first electrode 150 can be shielded by the first electrode 150, which may lead to a poor light-emitting efficiency of the whole LED chip 100. If the LED chip 100 has the current blocking layer 130, the light-emitting layer 124 located at a region under the current blocking layer 130 does not emit light or only emits few light, while the light-emitting layer 124 located at a region other than that under the current blocking layer 130 can emit light without being shielded by the first electrode 150. Therefore, waste of the power at the region under the first electrode 150 can be reduced by applying the current blocking layer 130.